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boiler taking on water

MPR Member Posts: 18
Hope everyone had a merry Christmas, happy Chanukah or what ever holiday you may happen to celebrate this time of year.

A few months back I wrote in with a question about my radiators spitting out water and everyone was such a tremendous help, well, knock on wood, but I think I've got that problem solved, now I have another question.

One of my radiators vents a lot of steam, and I've noticed that if I run the boiler for a long heating cycle that the automatic feeder will feed water into the boiler.  I left for Pennsylvania on Saturday morning and the autofeeder was showing 9 gallons and we turned our thermostat down to 59 degrees because we were going to be away.  Today when I got back we brought the house back up to 66 degrees and consequently the rads were working for a longish time (I should also mention that the rad in question vents a lot of steam even during our normal swings) and I went to check the boiler, as I have been doing regularly since learning about this site and I saw that the autofeeder was now at 10 gallons.

My questions are these:

I assume that if this rad is venting steam, it probably shouldn't be and that eventually this will lead to a decreased water level in the boiler thus causing the autofeeder to call for more water,

 one, is that correct?  and two, how can I fix that?


Single pipe steam, no underground returns, Burnham independence Boiler, Pressure set correctly and no leaks in the boiler from what I can tell.

Thanks in advance...


  • Jamie Hall
    Jamie Hall Member Posts: 22,924
    That vent

    should be looked at.  It may be the correct size, but a radiator vent should not leak or release steam -- when steam hits it, it should close.  It may just need to be cleaned, or it may need to be replaced.  But it shouldn't do that.

    With the change from the autofeeder reading "9" to reading "10" -- it may well have added a gallon sometime over the weekend.  This doesn't mean, however, that you lost a gallon over the weekend.  What it does mean is that you lost a gallon between the time it switched from 8 to 9 and now -- which is why you write the date down when it switches on the little card next to it.  The other way to keep a closer eye on things is to put a mark on the gauge glass -- I use a spring type clothes pin -- and look at it from time to time when the boiler is off, to see what's happening.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • MPR
    MPR Member Posts: 18
    Changed vents/problem still happening

    Alright, so I switched out the old hoffman A1 (1A?) vent and replaced it with a maid o mist #4, I want a slow vent in this room since it is the thermostat room and it appears the problem is still happening. 

    Could it be another problem other than the vent ,although I can't seem to troubleshoot what it might be.

    Or could I just be feeling the releasing air?  I held my finger over the vent hold where I could comfortably hold it without it burning and there was moisture on it, kind of like holding a finger over a whistling tea kettle vent.

    During this heating cycle, the rad was hot all the way across so I assume that it should have shut the vent down once the steam got all the way across the rad to the vent.
  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,576
    edited January 2012
    spitting steaming vent

    what is the pressure on your good low-pressure gauge [not the useless 0-30 psi, code required gauge]? please don't assume that just because the pressuretrol is set to "X" psi, the pressure is "x". the standard gauge is like having a 10,000 mph speedometer in your car, where it would not show movement of the needle below 100 mph!

    with elevated pressure, the returns are overfilled with water from the boiler by 1.75 inches per ounce, and that can cause the auto/over-feed to operate erroneously in compensation.

    at the low pressures these systems need, the main venting needs to be ample/generous/capacious/effective/extensive/voluminous/etc..--nbc
  • MPR
    MPR Member Posts: 18

    Unfortunately all I've got right now is the standard 0-30psi gauge.  The highest I've seen it go is about 2 psi.  Are you saying it could be running much higher than that?

    Also, the steam comes out of the vent with a steady and loud hiss.  It really pushes a lot of vapor out.  The problem I had with the spitting radiator and severe waterhammer earlier was fixed (i think).

    If I correctly understand what you're telling me it is that there may be water in the returns that is not making it back to the boiler causing the autofeed to call for more.

    How does too much pressure cause that to happen?
  • Abracadabra
    Abracadabra Member Posts: 1,948
    new vent leaking?

    you are getting steam vapor out of the new vent?
  • MPR
    MPR Member Posts: 18
    from what I can tell they are

    When I hold my fingers over the vent hole, they are damp, kind of like when you put your hand over a steaming pot or a tea kettle.

    I've bought a couple of new vents at the store, this maid o mist #4 is one of them, I'm going try some of the others to see if maybe this particular vent is defective.
  • MPR
    MPR Member Posts: 18

    it is only one vent that is doing this, not multiple.
  • Klaas
    Klaas Member Posts: 8
    Venting steam

    For a long time I had a radiator that would do that when the boiler had been running for a while.  Initially I "solved" the problem by taping a cork over it when it started going.  Embarrassing to admit...

    Once I started trying to actually fix it, though, nothing changed when I got a new vent or tried switching a vent from a radiator that was working fine.  What fixed it, I think, was turning down my pressuretrol.  I don't know why only that radiator was affected, but based on that series of events, I concluded that something about the configuration of that radiator made it so the vent couldn't close against the pressure it was seeing.  I could be off base, but since from previous comments it sounds like you might have too much pressure anyway, it might be something to consider.

    Note: I turned my pressuretrol down to about 1.5psi with a 1psi diff.  I have but haven't yet installed a low-pressure gauge, so I didn't want to crank it all the way down until I could have some insight into what it's actually doing in practice.
  • MPR
    MPR Member Posts: 18

    Thanks for the advice.

    I just went and lowered the pressure on my system too.  Unfortunately, it is pretty warm here in section of the Northeast where I live so I may have to wait a few days to see the result.
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